Accompanied with continual development of the electronic technology, various electronic products are becoming more and more compact and versatile with overwhelmingly diversified functions. Therefore, a large number of electronic components of all types need be provided in a chip having a relatively small area in order to meet actual requirements of the electronic products.
However, in certain circuit layout, it happens that the number of electronic components within a certain area gets too large, that is, a density of the electronic components of the area is too high, such that routing between the electronic components within the area becomes infeasible. The circuit layout not only fails to pass design rule checking but is also unable to function normally.
For example, refer to FIG. 1 showing a plurality of combinational cells (e.g. NAND and OR logic gates) and a plurality of sequential cells (e.g., flip-flops) of a circuit layout on a chip. The combinational cells are represented in c, the sequential cells are represented in s, the arrows indicate data flow directions, and the shaded grids are blockages or spacing between the cells.
In this embodiment, suppose the density of the electronic cells with respect to an overall space 1 is 70%; that is, the electronic cells including the combinations cells c and the sequential cells s occupy 70% of the overall space 1, and the blockages and spacing occupy the remaining 30% of the overall space 1. To have the circuit layout pass time constraint, the combinational cells c are mostly placed at a central area of the overall space 1, while the sequential cells s are mostly placed at outer areas of the overall space 1. As observed, in a congestive region 10, quite a number of combinational cells c are crowded together to result in congestion. As stated, with an excessively high electronic cell density, routing between the electronic cells can become extremely difficult that the circuit layout fails to pass design rule checking.
Therefore, it is one of the objectives to provide an apparatus and method of preventing congestive placement to overcome of aforesaid issues.